It has previously been attempted to manually withdraw and rotate a signal-producing-sensor probe through a zone of a tube which is desired to be inspected and to visually note the probe position while recording the signal from such inspection for analysis. The inspection has been performed by manually rotating an internally threaded hollow shaft to react against an externally threaded hollow shaft concentrically assembled therein. A probe tail including electrical and fluid supply lines extends through, and is clamped to, the internally threaded shaft, for rotation therewith. Since the probe and its tail are torsionally rigid, the rotation imparted to the probe tail, rotates the probe and twists the electrical and fluid supply lines. Because of the twisting, the rotation and the withdrawal motion must be periodically interrupted to manually untwist the supply lines. The inspection is thus interrupted. Moreover, because of the interruptions and manual rotation irregularities, backlash in the system creates acceleration, deceleration and other intermittent variables which may distort the signal to be recorded. This is especially so if the tube produces a variable resistance to rotation of the probe due to variations in friction, surface cleanliness, flaws and interruptions. For these reasons, these manual attempts have not been successful in providing a constant and reliable signal.
Accordingly, there has been a need in the art for an automatic indexer assembly which provides a constant axial and rotational movement of a signal-producing-sensor probe through a zone of a tube to be inspected and recorded for analysis.